1. Field of the Invention
This invention relates to a hydrogen storage alloy and, more specifically, to a hydrogen storage alloy with a narrow hysteresis and a maximum hydrogen concentration, (H/Lm (NixAlyMoz)), equal to 7.
2. Description of the Prior Art
After hydrogen storage alloys that can store and release hydrogen were discovered, researches on hydrogen storage alloys have been continuously advanced.
LaNi.sub.5 alloy, which was initially developed (see Japanese Laid-open Patent Application No. 51-13934) is advantageous in its great storage of hydrogen. However, La is considerably expensive, coupled with another problem that the alloy is liable to be broken into fine pieces when repeating storage and release of hydrogen and is prone to be corroded on contact with alkaline or acid solutions.
In order to overcome the aforementioned problem, there has been proposed the use of Misch metal (hereinafter referred to simply as Mm) wherein part of La is replaced by Ce, Pr, Nd or other rare earth metals, or a LaNi.sub.5 hydrogen storage alloy wherein part of Ni is placed by a metal such as Co, Al, Mn or the like. These proposals are set out, for example, in Japanese Laid-open Patent Application Nos. 53-4918, 54-64014, 60-250558, 61-91862 and 61-233969.
Nevertheless, a hydrogen storage alloy with high hydrogen capacity is still required. Accordingly, one purpose of this invention is providing a hydrogen storage alloy with a maximum hydrogen concentration, (H/Lm(NixAlyMoz)), equal to 7. “H/Lm (NixAlyMoz)” represents hydrogen storage capacities. For example, a H/Lm (NixAlyMoz) equal to 7 means each lattice unit of a hydrogen storage alloy can store 7 hydrogen atoms.
Besides, the other purpose of this invention is providing a hydrogen storage alloy; more specifically, the hydrogen storage alloy has a slight hysteresis such that the hydrogen storage device for filling the hydrogen storage alloy can stably execute hydrogen absorption/desorption reactions.